Question

A man swims to and fro along the bank of a river with a velocity v relative to water. If the velocity of flow is u, If he takes t1 and t2 to move to and fro journey respectively, the time taken by him to go down stream is ?​

Answer 1

Answer:

Speed of river, u

Speed of man relative to water,v

Downward speed of man w.r.t ground, v+u

Upward speed of man w.r.t ground, v−u

Downward time, t

1

=

v+u

s

and upward time t

2

=

v−u

s

Average speed = total distance/ total time

Average speed, V

av

=

v+u

s

+

v−u

s

s+s

=

v

v

2

−u

2

Hence, average speed is

v

v

2

−u

2

Explanation:

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